The present invention relates to a crankcase ventilation apparatus of an internal combustion engine of a motor vehicle, comprising an oil-mist separator for the separation of oil from the crankcase ventilation gas of the internal combustion engine and comprising an assembly for the return of lubricating oil from the oil-mist separator to an oil pan of the internal combustion engine, wherein the oil-mist separator comprises at least one preliminary separator and at least one fine separator, wherein the preliminary separator is connected to the oil pan via a first oil return flow passage allowing a continuous flow of oil there through during operation and wherein an oil collection chamber is provided downstream of an oil outlet of the fine separator, said oil collection chamber being connected to the oil pan via a second oil return flow passage which is equipped with a check valve to discontinue the flow of oil during operation.
DE 203 02 220 U1 shows a crankcase ventilation apparatus of the aforementioned type. Therein, the first oil return flow passage is designed in the form of an annular channel, with an oil outlet being provided adjacent to the bottom of the annular channel. The second oil return flow passage which comes from the oil collection chamber and is equipped with the check valve ends in the same oil outlet. This oil outlet is in communication with the oil pan of the associated internal combustion engine in a manner which is not described in more detail in this document.
DE 197 00 733 A1 shows a cylinder head cover which incorporates a two-stage oil-mist separator comprising a helical insert as preliminary separator and a fine separator arranged downstream of the preliminary separator. The oil separated in the preliminary separator and in the fine separator is supplied to a common single oil return flow hole in the bottommost part of the fine separator by virtue of gravity and is returned through this hole and into the engine oil circuit.
Where apparatuses according to the two documents mentioned above are concerned, crankcase ventilation gas may flow through the oil outlet or the oil return flow hole opposite to the oil flow direction provided and result in failures of the oil-mist separation. In order to prevent such failures, it is known per se to design an oil return line of an oil-mist separator with a siphon which forms a duct which is permeable to oil but tight to gas. To ensure reliable functioning of the siphon, it is, therein, essential that it contains the oil volume required for gas tightness and retains the oil volume during operation of the associated internal combustion engine.
To achieve this, DE 195 31 695 B4 proposes a crankcase ventilation of an internal combustion engine wherein an oil return line connects a pressure regulating valve to the crankcase via a check valve, wherein the oil return line comprises an oil collection chamber or siphon which is embedded in the crankcase or in a wheel house, wherein the oil collection chamber or siphon can be automatically filled with oil upon starting of the internal combustion engine, wherein the oil can be delivered by a scoop wheel or gear wheel arranged on a shaft, and wherein the housing encompassing the oil collection chamber or the siphon comprises an oil scraper nose. Although it is true that this arrangement provides for a continuous and automatic filling of the siphon, the internal combustion engine nevertheless requires special embodiments, namely the scoop wheel or gear wheel for delivery of the lubricating oil into the siphon and the oil scraper nose on the housing, which results in a high complexity and, thus, in high costs. Herein, significant inclined positions of the associated motor vehicle may, in addition, cause the oil collection chamber or siphon to be discharged, whereby the gas blocking function gets lost.
DE 199 48 163 A1 shows an apparatus for the ventilation of crankcases/cylinder heads of a combustion engine, comprising an oil separator and a return assembly for returning the separated oil into the crankcase. Therein, it is provided that the oil separator is arranged inside a line of an oil filling system of the combustion engine, the line serving to supply fresh oil into the crankcase. Therein, the return assembly, furthermore and preferably, comprises an oil-filled siphon-type section.
In this arrangement, the siphon is filled with oil while the engine is filled with lubricating oil for the first time. If required, the siphon is refilled with the oil separated in the oil separator during ongoing operation of the latter. However, this arrangement is considered to be to a disadvantage in that the free flow cross-section for filling in the fresh lubricating oil is considerably restricted by the arrangement of the oil separator and the siphon in the oil filling system, with the result that the oil can only be filled in at a low flow rate of the oil. Herein, there is the risk of fresh lubricating oil overflowing while oil is being filled in, resulting in fouling of the engine and contamination of the environment.